The proposed study is designed to use a variety of anatomical techniques to investigate the structural and functional organization of peptide systems in the vertebrate retina. These studies examine: 1) the localization and synaptic organization of peptide systems, 2) the postsynaptic sites of action of peptide systems and 3) the coexisting and interactive relationships of peptide systems. Initial studies have and will continue to concentrate on the enkephalins (enk), using the chicken, larval tiger salamander and teleost retinas as model systems. The specific objectives for the five year plan are as follows: 1) Light microscopic immunocytochemistry will be employed to examine the development of enk-amacrine cells in the chicken retina. 2) Light microscopic immunocytochemistry will be used to localize other enk-related opioid peptides in the chicken, larval tiger salamander and teleost retinas. 3) Enk-immunocytochemistry will be combined with backfill-labelling of ganglion cells to determine: 1) if enk-amacrine cells synapse onto ganglion cells and 2) if there exists enk-ganglion cells in the larval tiger salamander and goldfish retinas. 4) Light microscopic autoradiography will be utilized to determine the anatomical distribution of opiate binding sites in the chicken, larval tiger salamander and teleost retinas. 5) Multiple-labelling techniques will be employed at the light and electron microscopic level to examine enk's coexisting and interactive relationships with other peptide- and classical transmitter-specific systems. These studies will be performed in the chicken, larval tiger salamander and teleost retinas.